I am a beginner of CFX and i want to run a simulation of two phase flow. In the help document of CFX there is such a sentence that "Multiphase flows allow low speed compressibility effects to be modeled and you can mix compressible and incompressible fluids in one simulation."

But, in general, low speed flow can be regard as incompressible flow and compressible flow just mean high speed flow. So I want to know, in CFX ,low speed compressibility flow can simulate how fast velocity?